Couple of thoughts, for what they are worth.
If you do program a device that can trigger a charge after waking up and detecting interruption, make sure you protect against all of the weird edge cases that can happen when the altimeter is re-powered up later:
- After a number of hours, the weather will have changed the local ambient pressure, and the altimeter will wake to a higher or lower pressure by perhaps 25 feet per hour or more
- After traveling, the local pressure will be different by many feet of altitude
Also make sure that bench testing and power-down can't ever simulate an incomplete flight, or a subsequent flight might not work correctly.
In general be deliberate about which phases of flight are "resumable" and which are not. In general, be sure to restrict it to the boost and coast phases.
One creative fix to consider that can handle the exceptions above: add a separately powered real time clock of some type. I like Ambiq's—uses so few nanoamps that a capacitor can power them during a power blip. Then you can disallow resumption after a certain time has passed.
If that sounds like too much trouble, you could also make a poor-man's dead-switch timer with a capacitor and a discharge resistor that the MCU keeps charged up while running. Upon startup, the MCU first tests the voltage of the cap and if it's too low (in other words, it hasn't been kept charged recently enough), the MCU abandons the partial flight. Appropriate values of C and R can be set for whatever short time limit is desired.
The goal: absolutely prevent triggering after power up on the bench.
For what it's worth.